This invention relates generally to semiconductor devices and particularly to semiconductor devices in which leads used as a large number of input/output terminals are held on the inner surface of a metal support frame by way of a common insulating layer interposed therebetween.
Heretofore, DIP, FP, PLCC, and ceramic packages, for example, have been generally known as typical modes of package construction in semiconductor devices. In each of these packages, except for that of the lead-less chip carrier, the outer leads, which are the terminals for connection to the outside of the package, are so formed that each lead projects out independently for obtaining its individual electrical characteristic.
For this reason, each outer lead is in a state in which it can bend independently and therefore bends readily. Moreover, a precision of the relative positioning between leads of the order of only .+-.0.1 mm could be attained heretofore.
Furthermore, because of the need to prevent independent deforming of the leads, restrictions have been imposed on the lead material, lead thickness and width, and the pitch or spacing between the leads.
For example, in an FP (flat package), the minimum dimensions of the leads are at present a thickness of 0.15 mm, a width of 0.35 mm, and pitch between leads of 0.65 mm. For this reason, as the number of pins increases, the outer peripheral outline formed by the outer extremities of the outer leads of the package become large, and the size of the package accordingly has become increasingly large.
Because of the above mentioned restrictions, in the soldering process step during the process of mounting the semiconductor device on a printed wiring board or the like, a lead positional accuracy of the order of only .+-.0.1 mm can be attained at the present stage of the art, whereby particularly reduction of lead pitch distance has been difficult in general.
Furthermore, in the selection of the lead material, also, ample mechanical strength of this thin lead itself must be considered. In order to obtain this strength, the lead must have the high-strength characteristics of alloys containing nickel such as 42 alloy.